1. Field of the Invention
The present invention relates to an ophthalmologic photographing apparatus used in photographing a fundus of a subject's eye at an ophthalmologic clinic.
2. Description of the Related Art
Hitherto, two types of photographing methods, i.e., a mydriatic photographing method and a non-mydriatic photographing method, have been known as methods for photographing fundus images. According to the mydriatic photographing method, fundus photographing is performed by illuminating a fundus of a subject's eye with visible light at both of the time of observing the fundus of the subject's eye and the time of photographing thereof using a mydriatic. According to the non-mydriatic photographing method, fundus photographing is performed without using a mydriatic by illuminating a fundus of a subject's eye with infrared light at the time of observing the fundus of the subject's eye, and illuminating the fundus of the subject's eye with visible light at the time of photographing thereof.
Hitherto, the mydriatic photographing method and the non-mydriatic photographing method have been respectively performed using different apparatuses. Recently, an apparatus capable of performing both of the mydriatic photographing method and the non-mydriatic photographing method has been proposed.
Japanese Patent Application Laid-Open No. 9-140672 discusses a fundus camera in which an infrared filter is detachably arranged in an optical path extending from an illumination optical system, which illuminates a fundus of a subject's eye to be photographed, to the fundus of the subject's eye. An operator of this apparatus switches a mydriatic/non-mydriatic photographing mode selector switch of the fundus camera. Thus, the operator controls attachment/detachment of the infrared filter. Consequently, both of the mydriatic photographing method and the non-mydriatic photographing method can be performed using this single fundus camera.
On the other hand, there have been demands for storing, when the mydriatic photographing method of photographing a fundus of a subject's eye is performed using a mydriatic, information representing a pupil diameter together with image information at the time of photographing the fundus. Techniques for automatically measuring a value of the pupil diameter are discussed as conventional techniques effective for the purpose.
Japanese Patent Application Laid-Open No. 6-178762 discusses a perimeter for photographing a subject's eye using a photographing unit, such as a charge-coupled device (CCD), and for detecting a low-luminance portion on each scanning line while scanning photographed video signals, whereby a value of a pupil diameter can be detected based on a scanning time taken to scan the longest low-luminance portion among the low-luminance portions respectively detected on the scanning lines.
The fundus camera discussed in Japanese Patent Application Laid-Open No. 9-140672 is constructed so as to have the mydriatic/non-mydriatic photographing mode selector switch that an operator operates to select which of a mydriatic photographing mode and a non-mydriatic photographing mode is performed.
When an operation of the fundus camera is transferred to a mydriatic photographing mode, the fundus of a subject's eye is illuminated with visible light when the subject's eye is observed. However, in a case where no mydriatic is used, myosis of the subject's eye is induced. There is a minimum value of a pupil diameter photographable by each ordinary fundus camera. When the myosis of the subject's eye occurs, the pupil diameter thereof becomes less than the minimum pupil diameter. Consequently, the fundus of the subject's eye cannot be photographed.
At that time, it is necessary for photographing the fundus of the subject's eye to wait until the pupil diameter of the subject's eye, which is increased due to natural mydriasis, exceeds the minimum value of the pupil diameter photographable by the fundus camera. A time required by the pupil diameter to exceed the minimum value due to natural mydriasis varies with environment and differences among individual subjects. Thus, such a time may be several minutes. In such a time, the fundus of the subject's eye cannot be photographed. Consequently, efficiency in photographing the fundus is lowered.
Further, Japanese Patent Application Laid-Open No. 6-178762 does not discuss a method for adding the measured pupil diameter to image information. Thus, it is necessary for an operator to manually input the pupil diameter measured at the time of photographing. Accordingly, an operator may add an erroneous value to the image information due to an inputting error and may store the erroneous value added thereto.